Use a single jsonpath dialect

[willr3]

Feature idea.
Horreum currently uses a different jsonpath dialect for extracting the start and stop in addRunFromData than it does for all the Extractors. This effectively adds cognitive complexity to the user so that Horreum development is easier.

Horreum should provide a consistent means of defining jsonpaths across all features.

[willr3]

I think we have two options:

1. Extract the start and stop using postgresql's dailect by creating a database table where the data can be stored and the extractors can be tested.
2. Create something to translate between whatever jsonpath dialect we provide users and the various jsonpath dialects that are used within Horreum.

Option 1. is probably the easiest to implement but it maintains the hard dependency on Postgres.
Option 2 is the hardest to implement and honestly the only upside I see is it gives Horreum the ability to transition away from Postgres if needed.

I think options 2 is interesting but it would take a lot longer to implement and the benefit over option 1 is not something Horreum would use in the near term.